Searchers "currently suspect" that the AirAsia jetliner that disappeared Sunday morning over the Java Sea is on the bottom of the ocean, the head of the lead agency in the operation said today.

Interested in ?

Add as an interest to stay up to date on the latest news, video, and analysis from ABC News.

Add Interest

"We currently suspect that plane is located on the ocean floor," Bambang Soelistyo, the head of Indonesia's National Search and Rescue Agency said.

If the plane is found on the ocean floor, there would be a challenge in getting the plane to the surface because they do not have the "submersible" equipment, Soelistyo said.

The plane's Emergency Locator Transmitter should function automatically and send warning signals, but no signal has been detected by control centers in Indonesia or in neighboring countries, Soelistyo said.

Soelistyo confirmed that Indonesia's National Search and Rescue Agency is spearheading the search effort.

The AirAsia jet lost contact with air traffic control over the Java Sea during a flight to Singapore Sunday morning, shortly after the pilots requested a change of flight plan because of weather.

The Australian Defence Force deployed a Royal Australian Air Force
AP-3C Orion Maritime Patrol Aircraft to assist in the search, the Australian Department of Defense announced.

The Orion took off from Darwin Monday morning local time
to join the search operations.

Ships engaged in the search and rescue effort reached the area where the plane was believed to be lost around Belitung Island at approximately 6:49 a.m., a spokeswoman for the Indonesian National Search and Rescue Agency said.

Darkness and bad weather had forced the suspension of the search about 5:30 p.m. local time Sunday evening, said Indonesian transport officials.

Flight QZ8501, an Airbus A320-200, lost contact with air traffic control in Jakarta at 6:17 a.m. Sunday local time near Belitung Island, Indonesia, after the flight left Surabaya, Indonesian Air Transport Director Djoko Murjatmodjo said during a news conference Sunday.

The flight, which had at least 161 people on board, was scheduled to land in Singapore at 7:57 a.m. local time.

"We are deeply shocked and saddened by this incident," said Sunu Widyatmoko, CEO of AirAsia Indonesia. "We are cooperating with the relevant authorities to the fullest extent to determine the cause of this incident. In the meantime, our main priority is keeping the families of our passengers and colleagues informed on the latest developments."

Widyatmoko said the airline had mobilized a support team to help families of the passengers.

The flight was piloted by Captain Iriyanto, who had a total of 20,537 flying hours, according to a statement from AirAsia. More than 6,000 of Iriyanto's flying hours were on an Airbus A320.

The first officer, Remi Emmanuel Plesel, had 2,275 flying hours with AirAsia Indonesia, according to the airline.

ABC News consultant Col. Stephen Ganyard said weather may have played a role in whatever happened to the plane but several questions remained.

"We're looking for clues and at this point there are very few clues," he said.

The jet was flying at the regular cruising altitude for most jetliners - 32,000 feet - when the signal was lost, according to flight tracking website Flightradar24. No distress reports came from the plane, officials said.

A waiting area was set up at Changi Airport in Singapore, where the plane had been scheduled to land, with facilities and support for relatives and friends of the passengers on the plane. At Juanda International Airport in Surabaya, dozens of relatives sat in a room, many of them talking on mobile phones and crying. Some looked dazed, the Associated Press reported.

The White House said President Obama was briefed on the flight. A State Department spokesperson said the U.S. is "ready to assist in any way that's helpful."

This is the third air incident this year for Malaysian-based airlines.

Andy Wong/AP Photo

Relatives of passengers onboard the Malaysia Airlines Flight 370 that went missing on March 8, 2014, watch TV news about missing AirAsia flight QZ8501, during their year-end gathering at a house in Beijing, China Sunday, Dec. 28, 2014.

In July, another Malaysia Airlines jet was shot down over Ukraine, killing all 298 on board.

Very sad to hear that AirAsia Indonesia QZ8501 is missing. My thoughts are with the families. Malaysia stands ready to help.

In March, Malaysia Airlines flight 370, a wide-bodied Boeing 777 with 239 people on board, lost contact with air traffic control soon after taking off from Kuala Lumpur for Beijing. It hasn't been found.

Ganyard lamented the disappearance of another aircraft this year.

"It's really disheartening," said Ganyard. "It just shouldn't happen in this day and age."

Get real-time updates as this story unfolds. To start, just "star" this story in ABC News' phone app. Download ABC News for iPhone here or ABC News for Android here. To be notified about our live weekend digital reports, tap here.